Axially arranged rotary threshing or separating systems have long been in use in agricultural combines for threshing crops to separate grain from crop residue. These axially arranged systems typically include at least one cylindrical rotor rotated within a cage or concave, with the rotor and surrounding concave being oriented so as to extend forwardly to rearwardly within the combine.
During operation of the combine, crop material is fed or directed into a circumferential passage between the rotor and the concave. The crop material is carried rearwardly along a generally helical path through the passage by rotation of the rotor. As the crop material moves through the passage, grain is threshed from the crop material. Grain and chaff are separated out and drop into a cleaning system which separates the grain from the chaff. Stalks and other larger material that remain between the rotor and concave are discharged or expelled at a rear or downstream end of the rotor. Chaff that exits the cleaning system and crop residue that exits the threshing system are directed into a crop residue distribution system. The crop residue distribution system can include a rotary beater, chopper or other apparatus that conveys or chops the residue into smaller pieces and propels the crop residue rearwardly towards a distribution chamber or area at the rear end of the combine. Crop residue that enters the distribution chamber can either be discharged onto a field as a windrow, or directed into a spreader mounted on or at the rear end of the combine that is operable for spreading the residue over a swath of the field.
Crop residue that is discharged from conventional and axial combines onto fields often contains lost grain and seeds, including shrunken crop seeds and weed seeds. Most or all of the seeds are in the chaff that exits the cleaning system. Many of the seeds are not destroyed and remain viable after exiting the combine. Viable seeds can germinate and sprout in the field, resulting in the spread of undesired weeds and potential crop disease. Weeds that sprout are typically killed by tillage or chemical treatment. Weed control measures such as these can cost significant time and expense. Moreover, these weed control measures require additional equipment and additional equipment passes over the field. Additional equipment passes over the field can increase soil compaction and adversely impact the condition of the field.
Other weed control measures have included windrowing of chaff, followed by either burning or collecting the windrows before weeds can sprout. Weed control measures have also included pulling a large square baler behind the combine to contain seeds, or using an integrated continuous round baler. Examples of balers are described in U.S. Pat. Nos. 8,313,362 and 8,733,241, the contents of both patents being incorporated herein by reference in their entireties. These weed control measures also add significant time and expense, require additional equipment, and increase the number of equipment passes over the field. In addition, chaff has a low bulk density, making collection and transportation of the chaff material very inefficient.
To avoid discharging seeds into the field, some operators omit separation and cleaning steps during harvesting, and simply collect the grain and chaff together in the combine, without discharging the residue into the field. The combined grain and chaff (or “graff”) is taken from the field to a stationary recleaner to separate grain seeds, weed seeds and chaff by winnowing. This approach removes weed seeds from the field but requires transportation of the chaff material, which, as noted above, is very inefficient due to the low bulk density of the chaff. Processing using a stationary recleaner also generates residual material that must be handled.
The foregoing drawbacks of conventional weed control methods illustrate the need for more efficient and cost effective solutions for controlling weeds that sprout from crop residue.